Yahoo announced it is running the world’s largest Hadoop application, a 10,000 core Linux cluster producing data used by the Yahoo! Search Webmap.”. the numbers are really impressive:

• number of links between pages in the index: roughly 1 trillion links
• size of output: over 300 TB, compressed!
• number of cores used to run a single map-reduce job: over 10,000
• raw disk used in the production cluster: over 5 petabytes